Granular activated carbon alleviates the combined stress of ammonia and adverse temperature conditions during dry anaerobic digestion of swine manure

The effect of granular activated carbon (GAC) on batch dry anaerobic digestion of swine manure was studied under different temperatures and ammonia concentrations. At 20 °C, 35 °C and 55 °C, the digester was inhibited when the initial total ammonia nitrogen (TAN) concentration reached 2500, 3500 and 3500 mg/L, respectively. The degradation of protein at 20 °C decreased as ammonia concentration increased, but the process was little effected by ammonia at 35 °C and 55 °C. Results showed that when the initial TAN increased from 500 to 3500 mg/L, the TAN produced at 20 °C decreased by 526 mg/L, but it only decreased by 20 and 145 mg/L at 35 °C and 55 °C, respectively. Adding GAC improved the methane production rate by 8.4%–45.6%. Under adverse condition (20 °C and TAN = 3500 mg/L), GAC has the most positive effect on methane production. In which the maximum methane potential and maximum methane production rate increased by 38.8%, 34.1% respectively, the lag time shortened by 23.1%. The dominant bacteria at 20 °C and 35 °C were Tricibacter, Terrisporobacter and Clostridium_sensu_stricto_1, and Methanosaeta was the dominant archaea. At 55 °C, the dominant bacteria were Hydrogenispora and Ruminiclostridium_1, and the dominant archaea were Methanosaeta, Methanosarcina and Methanoculleus.